The present invention relates to methods that may be useful in treating subterranean formations, and more specifically, to improved methods of placing and/or diverting treatment fluids in subterranean formations.
Treatment fluids may be used in a variety of subterranean treatments. As used herein, the term “treatment,” or “treating,” refers to any subterranean operation that uses a fluid in conjunction with a desired function and/or for a desired purpose. The terms “treatment,” and “treating,” as used herein, do not imply any particular action by the fluid or any particular component thereof. Examples of common subterranean treatments include, but are not limited to, drilling operations, pre-pad treatments, fracturing operations, perforation operations, preflush treatments, afterflush treatments, sand control treatments (e.g., gravel packing), acidizing treatments (e.g., matrix acidizing or fracture acidizing), “frac-pack” treatments, cementing treatments, water control treatments, fluid loss control treatments (e.g., gel pills), and well bore clean-out treatments.
In subterranean treatments, it is often desired to treat an interval of a subterranean formation having sections of varying permeability, porosity, damage, and/or reservoir pressures, and thus may accept varying amounts of certain treatment fluids. For example, low reservoir pressure in certain areas of a subterranean formation or a rock matrix or proppant pack of high porosity may permit that portion to accept larger amounts of certain treatment fluids. It may be difficult to obtain a uniform distribution of the treatment fluid throughout the entire interval. For instance, the treatment fluid may preferentially enter portions of the interval with low fluid flow resistance at the expense of portions of the interval with higher fluid flow resistance. In some instances, these intervals with variable flow resistance may be water-producing intervals. In other instances, the portion of an interval with low fluid flow resistance may be an elbow or turn in a well bore, into which the treatment fluid may preferentially enter. In yet other instances, the portion of an interval with low fluid flow resistance may be a junction of a multi-lateral well, into which the treatment fluid may preferentially enter.
In conventional methods of treating such subterranean formations, once the less fluid flow-resistant portions of a subterranean formation have been treated, that area may be sealed off using variety of techniques to divert treatment fluids to more fluid flow-resistant portions of the interval. Such techniques may have involved, among other things, the injection of particulates, foams, plugs, packers, or blocking polymers (e.g., crosslinked aqueous gels) into the interval so as to substantially plug off high-permeability portions of the subterranean formation once they have been treated, thereby diverting subsequently injected fluids to more fluid flow-resistant portions of the subterranean formation.
While these diversion techniques have been used successfully, there may be disadvantages. For example, in many cases, at least some portion of the diverting material may be placed in the more fluid flow-resistant portion of the subterranean formation inadvertently, which may hinder or prevent the complete treatment of that portion. Moreover, in instances where a less fluid flow-resistant portion of the formation has been fractured, certain types of diverting agents (e.g., particulates) may not be able to effectively seal off the area without using large volumes of the diverting agent, which may be costly to place and/or difficult to remove.